The present invention relates to a sync signal generating apparatus for processing data stored in a disc sector unit, and more particularly to a system capable of detecting a sync signal and generating detected sync signal state information even though a sync pattern may not be present or there are disc sectors having damaged sync patterns.
Generally, data stored in a CD-ROM, CD-I, minidisc, and the like is stored in sector units of the disc. Such products scramble data to be stored in a sector unit in order to record it on a disc, and descramble the data read from the disc sector unit in order to reproduce the data. Accordingly, the disc reproducing apparatus necessarily must, for each sector, read out a sync pattern in order to reproduce the data stored on the disc.
FIG. 1A shows data with respect to a sector, FIG. 1B shows a clock signal utilized in processing the data, and FIG. 1C shows a detected sync signal obtained from the data, respectively. The sector illustrated in FIG. 1A consists of 2352 bytes, in which a sync pattern of 12 bytes is located at the beginning of the sector. When sync detection with respect to the sector is carried out, a detected sync signal SYNCDET is generated as illustrated in FIG. 1C.
However, conventional systems use only a sync detecting circuit for detecting the sync pattern of the reproduced data. Therefore, when the sync pattern is changed due to an error in the interim, or when no sync signal exists within the data read from the disc, such as when a track jump occurs, etc., these errors, which obstruct the reproduction, cannot be discriminated so that quick action can be taken by a controlling portion. Also, if the sync pattern is either changed or not detected, the sector interval of a sector undergoing descrambling is changed which impedes accurate reproduction of the data desired by a user.
A system capable of restoring the data from the disc sector regardless of whether a sync signal is missing or is damaged, is disclosed in European Patent Publication No. EP 549,151 A2 laid open on Jun. 30, 1993. Here, a selected sector is searched out in order to detect detecting a sync pattern that designates an arranged position of sector data. When such a sync pattern is not detected, a sync signal is detected by means of a window during a period corresponding to a sector data field. Then, when no sync is detected even after the period has elapsed, a sync find-fault signal is generated. In the case of failing in find the sync pattern, a pseudo-sync signal is generated by data restoration, and the window size is varied while moving a data block, thereby again detecting the sync signal.